Round balers have a bale forming chamber defined by an apron comprising an array of belts, chains, and/or rolls within which the cylindrical bale is formed. Crop material such as hay is picked up from the ground as the baler traverses the field and is fed into the chamber where it is rolled up to form a compact cylindrical package. Wrapping apparatus is provided for securing the package to form a bale while still in the forming chamber. The bale is then ejected from the chamber onto the ground for subsequent handling. A commonly known wrapping apparatus utilizes one or more twine dispensing arms for feeding twine to the circumference of the formed cylindrical package. Lateral traversal of the arm or arms results in a helical wrap around the package as it is turned in the chamber.
There are various prior art approaches for wrapping twine to maintain the compactness of the package when the bale is ejected. In most or all of these it is important that the initial free end of the twine strand, commonly referred to as the "tail",is consistently of sufficient length to assure that the wrapping operation is immediately and properly carried out. To accomplish this the twine is sometimes clamped after it has been severed at the completion of the previous wrapping operation. Clamping mechanisms are commonly utilized in the wrapping apparatus and in some instances are mounted on the twine arm to prevent loss or shortening of the tail due to slack in the system when the twine is cut.
Also of concern in twine wrapping apparatus is convenience of initially threading twine in a new baler or rethreading the twine when the supply becomes depleted. The twine is supplied from balls located in compartments on the baler. It is fed out of the compartments and guided along a path to the twine tube and ultimately to the dispensing end of the tube. During threading, the lead end is drawn along its path from the storage compartment and then through the wrapping apparatus. If clamps are employed they must be disengaged to permit threading and then reengaged to permit normal operation. When twine is pulled during wrapping from the dispensing tube it is desirable that it not be unduly impeded by such clamps disposed along its path.
Usually some kind of tensioning device is provided to apply tension to the twine as it is being wrapped around the package to improve bale compactness and stability. But, if such tensioning causes hesitation in the grasping of the tail, the wrapping start is delayed and baler reliability could be affected. Thus, controllable tension and tail length are important interrelated aspects of reliable round bale wrapping.